The acknowledged drugs of choice for the pharmacological treatment of insomnia are the benzodiazepine hypnotics, but the abuse liability of benzodiazepine hypnotics remains a critical issue. Presently there are insufficient and contradictory data regarding the abuse liability of benzodiazepine hypnotics. Numerous clinical reports of excessive use and dependence on benzodiazepines have been presented. However, the epidemiological and laboratory evidence suggests that the abuse liability of benzodiazepines is relatively low. Yet the fact that a relatively small percentage of persons may abuse benzodiazepines, suggests that specific conditions and/or personality characteristics place individuals at risk. Understanding the various risk factors will facilitate appropriate treatment of the many patients who have insomnia complaints. The aim of this research proposal is to document risk factors which increase the abuse liability of benzodiazepine hypnotics. Abuse liability will be assessed using controlled laboratory studies of the reinforcing and subjective effects of these drugs with concurrent objective measurement of sleep and wakefulness. Possible risk factors to be investigated have been identified from the epidemiological and the sleep disorders literature. Among the factors to be investigated are rebound insomnia, anxiety inappropriately focused on sleep difficulty, and expectations regarding sleep difficulty when discontinuing hypnotics. The degree to which these factors alter the probability of self administering a hypnotic will be documented and the extent to which self administration is unrelated to objective amounts of wakefulness will indicate non-hypnotic administration.